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MINI AND MICRO HYDROPOWER
DEVELOPMENTS
REPUBLIC of the FIJI ISLANDS
Arieta Gonelevu
Senior Scientific Officer
Our Ref: E 25 Fiji Department of Energy
01 October 2002
General Introduction of the Republic of the Fiji Islands
The Republic of the Fiji Islands is made up of more than 300 islands that is located in the
South Pacific Ocean at latitude 15o22S and longitude 174Eo177W. The group extends over
a total area of about 104,000 sq. km of which land occupies approximately 18,300 sq.km.
The two main islands are Viti Levu and Vanua Levu accounting for 58% and 34%
respectively of the total land mass. The total population of Fiji is 740,000 and it enjoys a
tropical climate with both dry and wet seasons over certain periods in a year. Fiji's
economy depends mainly on sugar and tourism.
The Fiji Department of Energy (FDOE) is responsible for national energy policies, energy
efficiency and renewable energy development, and rural electrification. Its mission is to
facilitate the development of a resource efficient, cost effective and environmentally
sustainable energy sector in Fiji.
The Fiji Electricity Authority is responsible for the development, generation, transmission
and distribution of electricity on the islands of Viti Levu, Vanua Levu and Ovalau. Since
the commissioning of the Monasavu Hydro-electric Scheme on Viti Levu in October 1983,
90% of Fiji's total electricity demand was met from hydropower resources generation from
the 80 MW Wailoa Power Station. Hydropower is a proven and mature form of renewable
energy but its future expansion in any form will have to take into account both
environmental and social issues.
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Hydropower
It has always been in the interest of FDOE to promote the use of renewable energy
resources and exploit these resources to provide high quality energy. For the island
populations, options for electricity generation will be limited to finding local island
solutions. FDOE has, over the decade, explored options for electrification of rural areas.
Due to its tropical climate, Fiji is well endowed with hydropower resources for
development of both large and small-scale hydropower projects. FDOE's Hydropower
Assessment Programme focuses on the following objectives:
To assess all potential mini/micro hydropower sites throughout Fiji and determine
their feasibility
To rank all potential sites within Fiji which would facilitate a more detailed
examination and subsequent development
Photo 1: Vatukarasa Mini Hydro
To ascertain the viability of the sites that have been identified and
To prepare pre-feasibility study reports for viable sites.
A countrywide study, undertaken by FDOE through ADB funding, identified close to 100
small-scale hydropower project potentials. These sites are now being studied by FDOE to
confirm their development potential for meeting small electricity demands. Needless to
say, Fiji has a significant large-scale hydropower resource potential. Fiji's next best option
for hydropower development is Vaturu Water Catchment Scheme followed by
Wainisavulevu/Wainikasou diversion. Significant hydropower development potential lies in
Fiji's largest rivers such as Sigatoka, Ba and Navua.
Based on the results of our Hydropower Assessment Programme, hydropower was
incorporated into the RE policy as an electrification option.
The most recent hydropower project, undertaken by FDOE, is the 30 kW Muana
Hydropower Scheme that was funded by the Korean Government through the Korean
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International Cooperation Agency (KOICA), at a cost of $US200, 000. The Government of
Fiji met the local costs. The project is for the electrification of three villages of
Naqaravutu, Wailevu and Muana in the southern coast of Vanua Levu in the Natewa Bay.
The three villages have approximately 136 households with a population of 600. The
three villages also host a primary school, a health center, grocery shops, community halls,
etc.
Developments of Mini/Micro Hydropower
Hydropower systems use the kinetic (motion) energy in flowing water to produce
electricity or mechanical energy. The water flow via channel or penstock to a waterwheel
or turbine where it strikes the buckets of the wheel, transforming the kinetic energy into
mechanical energy by causing the shaft of the waterwheel or turbine to rotate. When
generating electricity, an alternator or generator, which is connected to the rotating shaft,
converts the mechanical power in the motion of the shaft into electrical energy. The
electrical energy may be used directly, stored in batteries or converted from direct current
(DC) to alternating current (AC).
Mini hydropower systems generate between 100 and 1500 kW. Micro hydro systems
generate up to 100 W. The power available in a flow of water
Photo 1: Hydro Monitoring Equipments
depends on two factors:
The vertical distance the water "falls" referred to as head (measured in feet or
meters)
Flow rate, which is the volume of water flowing past a point in a given time
(measured in cubic feet or cubic meters per second)
Mini/micro hydropower electricity is an ideal energy option for the rural areas because of
its low operational, maintenance and repair costs. It produces clean energy and also it is
more secure and reliable when compared to other options especially for areas where
transmission of grid power is difficult.
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Hydrological data have been supplied by the PWD Hydrology Section at locations where
gauging of stream flows has been carried out in the past. However, in most instances no
previous stream gauging has been undertaken and flows at time of site inspections were
estimated and used in the design. Some of the sites have been examined in more detail
on the ground and approximate survey checks have been made to check available heads,
etc for the preliminary designs of some of the schemes.
At all sites further survey will be required before final design work can commence and
more accurate cost estimates derived. Likewise, more stream flow data should be
gathered, particularly during dryer periods to assess the firm energy available at the
individual sites.
Environmental impact as a result of the implementation of any of these schemes would be
marginal. Although the sites are relatively close to village centers, the village themselves
are remote. The aqueduct and penstock routes have been chosen to avoid unstable
ground and to avoid the occurrence of landslides, etc.
Survey Procedure
When villages request for hydro survey through the provincial office or to DOE, the survey
team list the villages and undertake field survey at the potential sites. Contents of
investigation are to measure the discharge at potential site and gross head
Photo 3: Weir Survey ¨C Kadavu Koro
between the potential site and the proposed powerhouse site ¨Cthe main purpose of this
part of the investigation is to collect the data in this dossier and data collected via these
surveys and investigations.
Following the filed survey, all potential min/micro hydro sites in the county will be ranked
to prioritize the sites for long-term hydrology (water level, rainfall, flow rate, etc.) data
accumulation for the three-year monitoring period.
Problems associated with small hydro development in Fiji
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The Fiji Islands generally have topographical and meteorological characteristics that
present a number of problems regarding small hydroelectric developments. Most parts of
the islands are subject to dry seasonal periods or dry periods between heavy rainfalls.
With the generally steep topography in areas where hydro sites might be expected there is
a rapid runoff and unless there is a considerable ground water feed to the stream,
discharge falls off rapidly to some base flow which may be very limiting as far as firm
power production is concerned.
On the other hand all parts of the island are subject to occasional very high rainfalls and
intensities, particularly during the passage of tropical cyclones near or over the islands,
which result in very sever flooding in the streams. These floods introduce certain
problems affecting the design, operation and maintenance of diversion and intake
structures. Although most streams considered fro these small scale hydro electric
developments convey naturally clear water during dry weather or even medium flows,
during flood discharges they carry a bed load of cobbles, gravel and sand as well as
floating debris which cause potential problems in small intake works. Furthermore during
high rainfall periods most catchments are subject to landslips in steeper areas and this
adds to debris carried down by the flood.
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